1. Field of the Invention
The present invention relates to a technique for detecting an object from an image.
2. Description of the Related Art
Conventionally, specific objects such as a face and a human body from an image captured by a monitoring camera are detected by a pattern matching process. Japanese Patent Laid-Open No. 2009-211311 describes an image processing apparatus which extracts a plurality of local patterns using a collation pattern in the entire region of an image while changing the size of the image, thereby calculating local feature amounts. This image processing apparatus determines whether the detected object is a human body, based on the sum total of the weighted local feature amounts.
As a method of speeding up a detection process for these specific objects, a method of switching the priority level of a reduced image (layer) used in pattern matching, based on the past image capturing results, has been described in Japanese Patent Laid-Open No. 2007-135115.
However, especially a monitoring camera mainly captures a wide range in the depth direction in most cases, and therefore often obtains a scene in which large and small objects are mixed in the same screen, so the objects do not always have the same size in this screen.
Under the circumstances, to detect all objects to be detected, it is necessary to use collation patterns corresponding to small and large objects. It is therefore eventually impossible to perform a detection process at high speed even when the priority level of a reduced image (layer) used in a collation process is changed.